| 摘要: | 本研究使用一長1.5公尺、寬0.1公尺、高1.0公尺的矩形玻璃流槽並使用氣壓缸進氣讓擋板快速抽離，讓事先填充好的顆粒柱模擬顆粒潰壩(dam-break)實驗，顆粒堆積柱在幾乎相同的初始寬高比(initial aspect ratio)下，使用不同長度的圓柱及改變圓柱含量占比來探討顆粒崩塌流運動狀態及流動性的影響。為了可觀察到顆粒崩塌的每一個特徵時間點的運動變化，使用高速攝影機並利用PIV技術(Particle image velocimetry)觀察顆粒崩塌流的運動變化及各特徵時間點下速度剖面的差異。
從實驗結果可知，當只含有少量圓柱顆粒時，因為圓球顆粒被替換成圓柱顆粒，整體的顆粒面積減少，但是圓柱顆粒因數量較少彼此距離較遠，顆粒互相牽引的特性此時並不明顯，並且因圓柱顆粒的存在破壞了顆粒堆積體的穩定結構，而造成了潤滑效果(lubrication effect)，而使其崩塌距離較遠，流動性也變得更好，於8mm組實驗中，圓柱顆粒含量為5%時有最遠的崩塌距離，而12mm組實驗則是在25%時有最遠的崩塌距離；但是若再持續增加圓柱顆粒含量占比，圓柱顆粒互相牽引的特性會越來越明顯，反而會造成結垢效果(fouling effect)，而使整體崩塌距離變短，流動性也變得較差。分析方面也藉由特定垂直斷面(δL/3+Li)的顆粒流動速度剖面來討論顆粒崩塌的速度變化，以及藉由改變圓柱含量占比來觀察對顆粒崩塌流流動性的增減。
;In this study, a rectangular glass chute with a length of 1.5 meters, a width of 0.1 meters, and a height of 1.0 meters was used, and a pneumatic cylinder was used to inhale the baffles quickly to allow the pre-filled particle columns to simulate a dam break experiment, under almost the same initial aspect ratio of the particle stacking column, using cylinders of different lengths and changing the content ratio of the column to investigate the impact of the particle collapse flow on the state of motion and fluidity. In order to observe the movement changes at each characteristic time point of the particle collapse, use a high-speed camera and use PIV technology (Particle image velocity) to observe the movement changes of the particle collapse flow and the difference in the velocity profile at each characteristic time point.
When only a small amount of cylindrical particles are contained, the particle area is reduced because the spherical particles are replaced by cylindrical particles, but due to the small number of cylindrical particles, the distance from each other is far away, and the characteristics of the particles′ mutual traction are not obvious, and because the existence of cylindrical particles destroys the stable structure of the particle accumulation, resulting in a lubrication effect, so that the collapse distance is longer, and the fluidity becomes better, In the 8mm experiment, when the cylindrical particle content is 5%, there is the farthest collapse distance, while in the 12mm experiment is 25%.; but if the cylindrical particles continue to increase, the characteristics of cylindrical particles pulling each other will become more obvious, which will cause fouling effect instead, shorten the collapse distance and make the fluidity worse. In terms of analysis, the particle flow velocity profile of a vertical section (δL/3+Li) is used to discuss the velocity change of the particle collapse, and to observe the fluidity of the particle collapse flow by changing the proportion of the column content. |
